In general, vehicle drivelines transmit torque from a vehicle's engine to its wheels. Automotive drivelines sometimes include power transfer units (PTUs, also known as power take-off units) for selectively distributing torque among shafts in the drivelines. The PTUs are often equipped in four-wheel and all-wheel automotive driveline configurations. A power transfer unit typically consists of a housing that encloses and supports gears, shafts, and bearings. Packaging in automotive drivelines, as elsewhere in automobiles, often demands inflexible size constraints. And sometimes the size constraints present challenges when designing PTUs to produce a desired torque output while still satisfying durability requirements imposed by automotive manufacturers.